Introduction

Group 1 of the periodic table -- lithium, sodium, potassium, rubidium, caesium and francium -- is called the alkali metal family because their hydroxides are strong alkalis (bases) that dissolve freely in water. Group 2 -- beryllium, magnesium, calcium, strontium, barium and radium -- is called the alkaline earth metal family because their oxides and hydroxides are also basic (alkaline), while several of the metals themselves (and their carbonate ores) occur abundantly in the earth's crust.

Both families belong to the s-block of the periodic table: in every atom of Group 1 and Group 2, the electron added last (on building up the atom by the Aufbau principle) enters an s orbital of the outermost shell. This single structural fact is the root of almost everything distinctive about their chemistry -- their low ionization enthalpies, their strongly electropositive (metallic) character, and their outstanding reactivity.

Being the most electropositive metals in the periodic table, none of the s-block metals is ever found free (uncombined) in nature; every one occurs only as a compound, usually a chloride, carbonate, sulfate or silicate mineral. Francium and radium are both intensely radioactive and occur only in trace, transient amounts, so the chemistry of Group 1 in practice means Li through Cs, and the chemistry of Group 2 means Be through Ba.

This chapter also folds in, alongside the metals themselves, a short account of hydrogen chemistry as it applies here: the three structurally distinct classes of hydride that different elements of the periodic table form (ionic, covalent and interstitial), the industrially important compound hydrogen peroxide, and the case for hydrogen as a fuel of the future. It closes with the specific biological importance of four of these elements -- sodium, potassium, magnesium and calcium -- inside living systems.